Question about friction

In my physics book it says: "If there were no applied force (F), then Static friction force will be 0."

What confuses me is this, what if an object was sitting on a conveyer belt moving at a 30 degree angle, for instance. What causes that object to remain on the conveyer belt? obviously the friction between the object and the belt? Am i mixing up coefficient of friction and static frictional force?

yeah but what if you change the material being used for the conveyer belt? Then obviously more variables (besides the weight of the object) are introduced. Let's say that a smoother surface is used. The object will now slide down.

Sorry, Arildno already answered your question. I answered something you did not ask, so I deleted it. What I said is not wrong, its just not addressing your question. (Find out the answer to your question first, before moving on to what I said. I dont want to confuse you).